ABSTRACT

Salt cavern gas storage has become one of the world's important natural gas strategic reserves and emergency peaking facilities. However, most salt cavern gas reservoirs in China are built in layered salt layers. After leaching, a large number of insoluble mudstones is loosely accumulated in bottom of the cavity, and occupies a large amount of storage capacity (1/3-2/3). After the first gas injection and brine discharge in the salt cavern, there is still 2-5m of water left to the bottom. Furthermore, there is still a large amount of water in the pores of insoluble mudstones, resulting in a large storage capacity loss. Therefore, it is urgent to explore the technique of secondary brine discharge to drain more brine away.

In this study, a lab simulated brine discharge device was set up. If conventional sand control screen is used, the brine discharge efficiency was quite low and a mass of mudstones plugged the pipeline. The permeability of the pipeline can be reduced to 0.1mD. The reason for the blockage of the pipeline is that the mudstone particles are loosely accumulated and can migrate into the pipeline with the fluid. To solve this problem, we propose to use the chemical cementation method to improve the efficiency of secondary brine discharge. In order to improve the mudstone porosity after cementation, a foam resin system with bisphenol A epoxy resin and corresponding curing agent was prepared. It can cure sand at room temperature and 80 °C in 4 days to form a porous solid with high conductivity. This solid formed by foam resin and sands has good sand control performance. Under a constant gas injection pressure (0.1MPa), the pipeline flow and sand production were tested, and the temperature resistance and salt resistance were also tested. The experimental results show that the measured permeability of the foam sand system can reach more than 15mD, the sand production can be controlled within 0.5% in the secondary brine discharge process and is greatly reduced. The foam resin system has good temperature resistance and salt resistance, and can still have good sand control and conductivity under the temperature of 20°C-80°C and brine concentration of 0-26%. This study provides a new idea for the secondary brine drainage and sand fixation of salt cavern gas storage.

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